12-Missing Neighbor
Might leads to call dropped due to bad radio conditions from serving cell
When approaching near cell 2 while attached by another serving cell 1 in dedicated mode [during a call], you notice
that cell 2 BCCH doesn't exist in GSM Serving + Neighbors window at all disappeared
Served by cell 12203 BCCH: 64 while radio conditions was getting bad, noticed 2 near-by cells [BCCH's: 83,728] but there BCCH's don't exist in GSM Serving + Neighbor window, they may be missing neighbors.
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13-Site-Cell Down
Site may be down due to 1 of the following 2 reasons:
-Power problem.
-Hardware problem.
1-Power problem:
Under a cell but the Rx-Level from its BCCH in GSM Serving + Neighbors window is too bad, this problem may be due
to wrong antenna tilting or due to VSWR alarm in site.
2-Hardware problem:
Cell on TEMS map but when moving near to it, you didn't find its BCCH in GSM Serving + Neighbors window [even
while in Idle mode] so cell is not missing neighbor for sure but it is not serving as it is down.
Under site PRTSAID-TWN but you notice both sectors BCCH's [61, 43] are not exists in GSM Serving window as site is
down during drive test.
14-Dropped Calls
During a call on TEMS, your call is suddenly dropped and you hear call dropped on TEMS.
Call is dropped due to only 1 reason which is the bad radio conditions [level or quality] from your serving cell, which may occur due to any of the following reasons:
Bad radio conditions between your MS and the network is the only reason that may cause a call to drop, but the question is why you remained on your serving cell until radio conditions turned bad, why you didn't perform H.O to any neighboring better cell ?!
For sure you tried to perform H.O but this H.O may was delayed or failed or you couldn't perform H.O as the neighboring cells to you were not defined as neighbors [Missing] to your serving now cell, so you remained on serving cell until call is dropped.
So, dropped calls may occur due to 1 of the following reasons:
-No or delayed H.O.
-H.O failure.
-Missing Neighbor to your serving cell.
-Ping-Pong H.O.
We already proceed in all these 4 reasons in our before demonstrations.
NOTE: Any dropped call occurred due to [No service (Channel release)] in layer 3 messages on TEMS is considered to be due to bad radio conditions from serving cell [Level or quality], BUT as for reasons like [Abnormal network release – or any other messages, etc.] in layer 3 messages, you should differentiate if a dropped call occur due to any of these messages while:
-Radio conditions were bad, then this call is dropped due to bad radio conditions.
-Radio conditions were good, then this call is dropped due to sudden hardware problem on serving cell BTS which is not RF [Radio] problem.
15-TCH [Traffic Channel] Problem;
In GSM hopping channels window, you find a problem in a specific TCH [Traffic Channel] while other TCH's in hopping window are good which will be due to 1 of the following reasons:
-Cross feeder on TCH.
-Faulty DTRU [Hardware problem].
-DL interference [Co. or Adjacent].
1-Cross feeder on TCH:
Noticing bad Rx-Levels for specific TCHs in GSM hopping channels window while C/I value is fair in front of site sector's main beam, the feeder carrying this TCH from TRX to antenna may be switched and fixed in another sector antenna causing this bad level for this TCH.
2-Faulty DTRU:
Noticing bad Rx-Levels for specific TCHs in GSM hopping channels window while under site, this may be due to cabinet TRX-DTRU card hardware problem which generates power for these TCHs.
NOTE: You have to make sure that these TCHs Rx-Levels aren't bad because of cross feeder problem that these TCHs power are not being transmitted in another region with good levels before deciding that it is DTRU card hardware problem.
3-DL interference [Co. or Adjacent]:
Noticing bad C/I values for specific TCHs in GSM hopping channels window while Rx-Levels for same TCHs are good, this may be due to DL [Co. or Adjacent] channel interference affecting these TCHs causing high level of interference on them in down link.
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Prepared by:
Eng. Abdelrahman Ashraf Mostafa
abdelrahman_ashraf@hotmail.com